Thermoplastic resin films have been widely used as packaging materials and as other materials such as various industrial materials including label, graphic, OHP, mold-releasing, ink ribbon, electric insulator, heat-sensitive stencil sheet and stamping materials and magnetic materials including audio, video and data storage materials. In these applications, the film is generally used as a supporting member, and subjected to various surface treatments such as printing, vapor deposition, sputtering, plating, laminating and coating treatments. For this reason, from the view point of handling, the film to be used as the supporting member needs to have an appropriate rigidity. Moreover, in order to process the film with high precision even under high temperatures, it is essential for the film to exert a superior dimension stability under high temperatures.
In many cases, the film is molded through various methods, such as vacuum-molding, vacuum air-compression molding, plug assist vacuum air-compression molding, press molding and in-mold molding methods. In other words, the film is required to simultaneously achieve a high molding processability which appears to be impossible to provide simultaneously with the rigidity and dimension stability. In recent years, there have been strong demands for molded products which have more complicated and deeper shapes while maintaining a printed pattern with high precision and a glossy appearance, in a wide range of applications.
Patent Document 1 has disclosed a film that is superior in dimension stability under high temperatures as well as in moldability and surface processability. In recent years, however, in printing treatment processes and the like, films have been used under higher temperatures, raising a problem in that the conventional film is not applicable. Moreover, another problem is that, although the heat shrinkage in the width direction can be reduced in a film manufacturing process comparatively easily, it is difficult to reduce the heat shrinkage in the longitudinal direction.
Here, various films in which multiple thermoplastic resin layers are laminated have been proposed; for example, a product in which a laminated film with multiple layers that is superior in tearing resistance is bonded to a glass surface so that it becomes possible to effectively prevent glass from damages and scattering has been proposed (see Patent Document 2 and Patent Document 4), and a film in which resin layers having different indexes of refraction are alternately laminated into a multi-layered film so that specific wavelengths are selectively reflected has been proposed (see Patent Documents 5 to 9).
However, these films are insufficient in the dimension stability under high temperatures and tend to fail to provide a sufficient moldability.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-11217    [Patent Document 2] U.S. Pat. No. 5,604,019    [Patent Document 3] Japanese Patent Application Laid-Open No. 10-76620    [Patent Document 4] Japanese Patent Application Laid-Open No. 3-41401    [Patent Document 5] Japanese Patent Application Laid-Open No. 4-295804    [Patent Document 6] PCT Application WO No. 95/17303    [Patent Document 7] Japanese Patent Application Laid-Open No. 11-188810    [Patent Document 8] Japanese Patent Application Laid-Open No. 2000-141567    [Patent Document 9] Japanese Patent Application Laid-Open No. 2000-329935